1. Field of the Invention
This invention relates to a work-clamping unit for use in machine tools, and more particularly, to a hydraulically operating clamping unit allowing a plurality of works to be loaded thereon, the units being replaceable one after another on the table of the machine tool when the works are finished in machining.
2. Description of the Prior Art
In machine tools it is necessary to hold a work or works on the table (sometimes in the vise). When the machine tool is for a single specific purpose, such as drilling and planing, the works are the same in size and shape. This makes it possible to employ a standardized clamping device, and the clamping operation is simple and easy. But when the machine tools are for all purposes, the works are various in size and shape; generally, smaller works are handled for mass production. To handle a number of small works, the mechanism of the clamping device tends to be complicated. Recently N.C. (numerical control) machine tools are in wide use for mass production. Under the operation of N.C. machine tools it has been found that the work clamping requires much time, thereby negating the efficiency of the machines. During the work clamping the machines are at rest. In the light of their expensive prices it is uneconomical, which will be reflected in the prices of products.
To overcome this problem, proposals have been made for automatic clamping operation to meet the requirements under the numerical control. But no successful models have been achieved.
The present invention aims at solving the problems pointed out above with respect to the conventional clamping devices, and has for its object to provide an improved work-clamping unit capable of handling works of relatively small size and of various shapes.
Another object of the invention is to provide an improved work-clamping unit replaceable one after another when each machining operation is finished, thereby enabling the machine tool to operate with the minimum rest.
A further object of the invention is to provide an improved work-clamping unit having a base plate normally used as the clamping plane but usable as the working table even when the plane lacks the works in places. Therefore, it is not necessary to suspend the operation of the machine.
Other objects and advantages of the present invention will become more apparent from the following description when taking in connection with the accompanying drawings which show, for the purpose of illustration only, embodiments in accordance with the present invention.